Ahead of the talks, Western officials urged Tehran to meet international concerns about its nuclear activities.

Invoking possible military confrontation over Iran's nuclear defiance, British Defense Secretary Liam Fox said Saturday that the Geneva talks need to make a serious start toward resolving the issue.

"We want a negotiated solution, not a military one - but Iran needs to work with us to achieve that outcome," he said. "We will not look away or back down."

US Secretary of State Hillary Clinton said it was up to Iran to restore trust about its nuclear intentions, urging it to come to Geneva prepared to "firmly, conclusively reject the pursuit of nuclear weapons."

German Foreign Minister Guido Westerwelle said a nuclear-armed Iran "was unacceptable for us."

Since Iran's clandestine enrichment program was discovered eight years ago Iran has resisted both rewards - offers of technical and economic cooperation - and four sets of increasingly harsh UN sanctions, meant to force it to freeze its enrichment program.

Member states of the Nuclear Nonproliferation Treaty have a right to enrich domestically and Iran, which is a signatory, insists it is doing so only to make fuel for an envisaged network of reactors and not to make fissile warhead material.

But international concerns are strong because Tehran developed its enrichment program clandestinely and because it has deemed closed an IAEA probe meant to follow up on suspicions that it experimented with components of a nuclear weapons program - something Iran denies. Iran says claimed experiments are "fabrications" by the CIA that was provided to the agency.

Israel has threatened to attack Iran, even though Israel is believed to have stockpiled more than 200 nuclear weapons and it is not a member of the Nuclear Nonproliferation Treaty.

Sunday's announcement by Iranian nuclear chief Ali Salehi further burdened the pre-talk atmosphere, adding to tensions left by the assassination last week of a prominent Iranian nuclear scientist and the wounding of another.

Salehi said Iran had for the first time delivered domestically mined raw uranium to a processing facility - allowing it to bypass UN sanctions prohibiting import of the material.

Salehi, head of the Atomic Energy Organization of Iran, said the uranium ore concentrate, known as yellowcake, was produced at the Gachin uranium mine in southern Iran and delivered to the uranium conversion facility in the central city of Isfahan for reprocessing.

Salehi said the delivery was evidence that the mysterious bombings targeting the two Iranian nuclear scientists would not slow the country's progress.

"Today, we witnessed the shipment of the first domestically produced yellowcake ... from Gachin mine to the Isfahan nuclear facility," said Salehi, whose comments were broadcast live on state television.

Iran acquired a considerable stock of yellowcake from South Africa in the 1970s under the former US-backed shah's original nuclear program, as well as unspecified quantities of yellowcake obtained from China long before the UN sanctions.

Western nations said last year that Iran was running out of raw uranium as that imported stockpile diminished and asserted that Tehran did not have sufficient domestic ore to run the large-scale civilian program it said it was assembling.

But Salehi, who is also the country's vice president, denied that local stocks were lacking and said the step meant Iran was now self-sufficient over the entire nuclear fuel cycle - from extracting uranium ore to enriching it and producing nuclear fuel.

He added that the message to those meeting with Iran in Geneva on Monday and Tuesday was that they cannot stop Iran's nuclear work.

"No matter how much effort they put into their sanctions ... our nuclear activities will proceed and they will witness greater achievements in the future," he told state-run Press TV.

Salehi said the activity will be carried out under the supervision of the International Atomic Energy Agency, adding a bigger uranium mine at Saghand, in central Iran, will be inaugurated "in the not too distant future."

The Gachin uranium mill near Bandar Abbas processes ore extracted from a nearby mine into yellowcake. The processing is part of the early stages before actual enrichment of uranium.

Yellowcake is then taken to the Isfahan facility to be processed into uranium hexafluoride, which later can be turned into a gas used as feedstock for enriching uranium.

Uranium enriched to low grades is used for fuel in nuclear reactors, but further enrichment makes it suitable for atomic bombs.

Salehi did not provide details on how much yellowcake had been transferred to Isfahan, but said the shipments from now on would be carried out "continuously." State TV showed a large, covered truck apparently carrying the yellowcake.

In October, Salehi said nuclear experts have discovered larger uranium reserves than previously thought at Gachin and were stepping up exploration of the ore.

The Iranian government also has provided funds to its nuclear agency to begin ore extraction at Saghand, the mine with the largest uranium reserves in the country. Saghand has not yet become operational.